Method of repairing knife edge fins in spacer fluid seals

ABSTRACT

Disclosed herein is a method for the repair of knife edge fins generally utilized as spacer fluid seals in, for example, compressor and turbine rotating and stationary members. The knife edge fins become worn after extreme use through subjection to high temperature, corrosive gases and abrasive contacting, so as to require frequent replacement thereof. The method disclosed herein eliminates the necessity of replacing the entire knife edge fin and spacer or other apparatus upon which the fin may be mounted through a means of repairing the same.

United States Patent McDonald et al.

METHOD OF REPAIRING KNIFE EDGE FINS IN SPACER FLUID SEALS Inventors:George L. McDonald, 6806 E. 74th,

Tulsa, Okla. 74l 33; Michael L. Jackson, 22l6- /z N. Sheridan, Tulsa,Okla. 74115 Filed: May 11, 1972 Appl. No.: 240,829

US. Cl 277/9, 29/401, 29/DIG. 34, v 277/1, 277/236, 287/23 Int. Cl F16j15/16 Field of Search 277/1, 9, 11, 236; 29/401, DIG. 34

References Cited UNITED STATES PATENTS 2/1959 Engstriim 29/401 X 9/1964Connors et al. 29/401 3/1964 Ennis 277/1 Nov. 13, 1973 3,537,713 11/1970Matthews et a1. 277/55 3,637,223 1/1972 Weber 277/236 X 3,694,88210/1972 Desmond 23/D1G. 34

Primary Examiner-Charles W. Lanham Assistant Examiner-D. C. Reiley, IIIAtt0rneyCharles S. Holmes [57] ABSTRACT Disclosed herein is a method forthe repair of knife edge fins generally utilized as spacer fluid sealsin, for example, compressor and turbine rotating and stationary members.The knife edge fins become worn after extreme use through subjection tohigh temperature, corrosive gases and abrasive contacting, so as torequire frequent replacement thereof. The method disclosed hereineliminates the necessity of replacing the entire knife edge fin andspacer or other apparatus upon which the fin may be mounted through ameans of repairing the same.

10 Claims, 5 Drawing Figures PATENTEUHUV 131915 3.771. 798

SHEET 2 [F 2 25 fl zo METHOD OF REPAIRING KNIFE EDGE FINS IN SPACERFLUID SEALS BACKGROUND OF THE INVENTION The modern advent of gas driventurbines and com{ pressors, non-turbine apparatus requiring sealing, andother apparatus containing knife edge fins has found that rapiddegradation'of the metals utilized within the 1 turbine, compressor andother gas driven rotating bodies is experienced. This wear causesdestructive metallic wear and necessitates the frequent replacement ofmetallic parts containing the knife edge fins or fluid seals containedwithin the apparatus. The critical tolerances and strengths of materialsrequired for repairing knife edge fins and the associated apparatus haveobviated the development of any method by which the destroyed ordegradated knife edge fins may be repaired without necessitating thecomplete replacement of the apparatus upon which the knife edge fin iscontained.

Conventional replacement techniques, for example welding, precipitationof metals, destructive fissure regrowth, electron beam welding andplasma welding have all been found to be unacceptable for thereplacement of extreme tolerance knife edge fin members. In particular,it is extremely difi'icult to determine the degree of destructivefissuring or whether material concentration of metals contained withinthe repaired knife edge has occurred without requiring extreme testingwith the component from which the knife edge fin was removed. Generallydestructive testing is necessitated in order to adequately determinewhether or not the fin is sufficient for utilization within the turbine,compressor, or non-turbine apparatus. Conventional testing by X-raysdiffraction and other non-destructive inspection techniques have beenfound unreliable to determine whether or not a sufficient weld orprecipitation of metals thereon the component has been obtained. Theunreliability of the tests coupled with the extent of the extremeoperating conditions of the knife edge fins are extremely difficult toovercome. For example, the knife edge fins used on spacers in theturbine section of an engine operate at conditions in excess of 2000revolutions per minute under low compression and a similar spacer may beutilized .in acompressive section of a jet engine operating under highcompression in excess of 2,000 rpm. These extremes in operation requirethat the part have .high mechanical properties and gain lastingperformanceas if a new part had been substituted for the damaged part,which had undergone previous degradation during engine wear.

Therefore, what is required is a methodand resulting apparatus for thereplacement of knife edge fins upon apparatus which may be reused withina compressor, turbine or other apparatus without requiring completereplacement of the repaired part. 7 It is the object of the presentinvention to provide a method for the repair of knife edge fins.

It is a further object of the present invention to provide a methodwherein knife edge fins or air seals may fins upon the apparatus forwhich replacement is desired.

It is'still a further object of the present invention to provideapparatus which may be formed from a part requiring repair orreplacement through the utilization of a method for the repair of thedegradated knife edge fin in order'to provide apparatus which willafford continued usage.

, With these and other objects in mind, the present invention may bemore readily understood by referral to the accompanying drawings andfollowing description:

SUMMARY OF THE INVENTION The present inventionprovides a method forrepairing a metallic and non-metallic knife edge fin or fluid seal, saidin being formed of a sharpened blade, formed as a part of a componentpart to be sealed. which comprises the steps of honing the knife edge orthe blade to form a flat surface thereacross the normally sharp blade. Asubsequent step is provided of reaming a groove in the upper portion ofthe blade through .the flat surface and placing a metallic wedge in thegroove, said wedge having a height which in combination with the heightof the blade forms a blade of the exact height of the blade of theoriginal knife edge. The upper portion of said blade being sharpened toform a knife edge, an additional step is performed of crimping the sideof the blade to close the groove about the wedge. When repairing a finon the outer surface diameter of a part, the methodmay further compriseheating the blade and groove contained therein, prior to theintroduction of the wedge, and then cooling the wedge prior to itsintroduction into the groove so that the thermal coefficient ofexpansion will expand the groove and contract the wedge such that a firmthermal fit may be formed during the cooling of the groove and theheating of the I wedge. A similar method may be utilized .for replacingfins on the inside diameter of a part.

In a preferred embodiment of the present invention a process is utilizedwherein the knife edge fin is circular and the wedge is a circular bandhaving'a flat inner circumferential edge, andthe externalcircumferential edge being sharpened to form a knife edge. In generalitispreferred that the circular band have a greater malleability thatthat of the circular metallic knife edge fin. It is further preferredthat the circular band exhibit a lower Youngs modulus than the circularmetallic knife edge fin. Should the metallic knife edge finbe precast,it may bemade more malleable than the circular band by malleabilizin'gthe casting by. annealing the casting to convert the chemically combinedcarbon contained therein, at least partially, into free graphite carbonin rounded form.

The object of the present invention may further be accomplished throughapparatus comprising a rebuilt metallic knife edge fin, said sealoriginally being formed of a sharper blade formed as a part of thecomponent part to be sealed and the apparatus comprising a honed knifeedge of the blade forming a flat surface having a groove reamed therein,and a metallic wedge having a sharpened upper portion thereof forming aknife edge and the lower portion thereof being crimped within the grooveof the blade. Ina preferred embodiment of the'present' invention, theapparatus'may comprise a knife edge, fin circular and the wedge being berepaired through a reconstruction of the 'knife edge formed ina.circular ring having a'flat inner circumferential edge and an externalcircumferential edge being sharpened to form a knife edge.

BRIEF DESCRIPTION OF THE DRAWINGS The application of the method andresulting apparatus of the present invention may be more readilyunderstood by referral to the accompanying drawings, in which:

FIG. 1 represents a cross sectional view of a compressor section of ajet propulsion engine showing the disposition of several knife edge finsutilized as gas seals on a spacer band within the compressor section ofthe jet propulsion engine;

FIG. 2 illustrates a side view of a spacer band as taken along line 1,1of FIG. 1 depicting thereon the knife edge fins utilized in order toseal hot gases passed through the compressor section;

FIG. 3 represents a cross sectional side view of a knife edge finassembly as positioned upon the upper portion of a spacer band or otherapparatus utilized in order to seal gas movement;

FIG. 4 depicts a partially repaired knife edge fin, as repaired by themethod of the present invention, having a sharpened wedge positionedwithin a honed, degradated knife edge fin; and

FIG. 5 represents the apparatus of the present invention depictingtherein the knife edge fin as repaired upon the spacer band, or othercomponent upon which the repaired knife edge fin is positioned, in orderto provide a repaired knife edge fin for further utilization.

DETAILED DESCRIPTION OF THE INVENTION The present invention involves amethod, and apparatus formed by the same, for repairing degradated knifeedge fins which have been damaged through operation under severeoperating conditions. The repair operation is utilized wherein normallythe component part upon which the knife edge fin is mounted must bediscarded with new apparatus being required as a replacement part. Inthe method of the present invention, for repairing a metallic knife edgefin or gas seal, the fin is generally formed of a blade and a sharpenedknife edge section contained thereon the blade. The knife edge fin andits disposition therewithina compressor or other related apparatus maybe more readily depicted by referral to the accompanying figures.

In particular, in FIG. 1 is depicted a compressor section of a jetpropulsion engine containing therein compressor fins 11, pivotallyconnected through pins 14 and arm 12 of compressor fin 11 to compressorarm 15, attached to the compressor rotor not depicted in FIG. 1. Ahousing shield 17 is shown extending therein the compressor sectionforming a gas space 18 therebetween the housing 17 and the compressorarm and fin 11 so as to require gas flow sealing at the surfacescontained between the housing 17 and the compressor fin 11. The gas sealis formed through introduction of spacers 21 and 16 having thereon knifeedge fins 22 and 25, respectively. The knife edge fins 22 and 25 contactthe upper edge of the compressor fin 23 and the lower edge of thehousing arm 24, respectively, so as to form a gas seal. The gas sealandknife edge fins are exaggerated in dimension to illustrate theirposition.

The introduction of the knife edge fins 22 and 25, respectively, causethe hot gases from the jet propulsion engine to be forced against thecompressor fins 1.1, not

allowing gas to circulate through the exaggerated clearances between thespacer 21 and the upper edge of the compressor fin 23 and the spacer l6and the lower edge of the housing arm 24. The forced gas flow requiresthe compressor fin 11 and arm 15 attached thereto, to rotate, causingthe drive momentum of the jet propulsion engine.

The particular disposition of the knife edge fin upon a circular spaceris more readily depicted in FIG. 2. FIG. 2 being a cross sectional viewtaken along line 1,1 of FIG. 1 illustrating the spacer band 16 as shownhaving weight-reducing and metal-saving holes 29 contained therein, saidholes 29 affording expansion of the spacer band 16 and reduction inertiathereof. The spacer band 16 has mounted on a circumferential surfacearea thereof a blade 25, and knife edge 19 contained thereon, forforming a knife edge fin or gas seal of the present invention. Asdisclosed the knife edge fin is subjected to tremendous operatingconditions and often is exposed to corrosive operating conditionsrequiring the knife edge fin to be formed of materials having highabrasive wear characteristics. Unfortunately, often these materials areeasily degradated under the tremendous operating conditions required forthe usage of the knife edge fin requiring frequent replacement of thepart upon which the knife edge fin is contained. Replacement of theknife edge fins being both expensive and time consuming requiring a newpart to be relocated within the apparatus from which the worn knife edgefin is removed.

By referral to FIG. 3, a cross sectional view of a blade 25 and knifeedge 19 contained thereon a spacer band 20, illustrates a knife edge finto be utilized for a fluid seal. The method for repairing a metallic ornonmetallic knife edge fin of the present invention, may be more readilyunderstood through a knowledge of the formation of a blade 25 and knifeedge surface 19. In particular, when degradation of the knife edgeoccurs, for example, the broken knife edge 30 depicted in FIG. 3, repairor replacement of the component is required. The initial step of themethod of the present invention comprises honing the knife edge 19 oftheblade 25 to form a flat surface thereacross the normally sharp blade 25.By referring to FIG. 4, the honed knife edge and blade may be morereadily disclosed as having a flat surface 26 contained thereupon blade25 of spacer 20. A groove 27 is reamed in the upper portion of the blade25 across the flat edge 26. A metallic wedge 28 is positioned within thegroove 27, said wedge 28 having a height, which in combination with theheight of the blade 25, forms the knife edge fin of the exact height ofthe blade 25 and knife edge 19 of the original knife edge fin asdepicted in FIG. 3. Said upper portion of the wedge 28 is sharpened toform a knife edge. Subsequent to the positioning of thewedge 28 withinthe groove 27 of the honed blade 25, the sides of the blade 25 arecrimped in order to close the groove 27 about the wedge 28 as depictedin FIG. 5. The crimping operation forms a repaired and improved knifeedge fin comprising a wedge 28 crimped within the groove 27 of the blade25 having the fiat honed surface 26 now crimped in an angled position soas to form a smooth, contoured knife edge fin upon the surface 20 of thespacer band or other object being repaired.

As previously disclosed, the method of the present invention may providean apparatus comprising arebuilt metallic or non-metallic knifeedge'fin. In general,

the knife edge fin is originallyformed of a sharpened blade formed as apart of a component to be sealed with the improved apparatus comprisinga blade having a honed knife edge forming a flat surface and having agroove reamed therein.

As depicted the knife edge fin may be circular and the wedge comprise acircular band having a flat inner circumferential edge, the externalcircumferential edge being sharpened to form the knife edge. It isgenerally preferred that the circular band have a greater malleabilitythan the circular metllic knife edge fin and included blade, with thecircular band exhibiting a lower Youngs modulus than the circularmetallic knife edge fin and included blade. Within the operation of themethod of the present invention, the metallic knife edge fin andincluded blade may be precast and made more malleable than the circularblade by malleabizing the casting by annealing the casting to convertthe chemically combined carbon contained therein, at least partially,into free graphite carbon in rounded form. Malleabilizing may beobtained by subjecting the casting under a nitrogen atmosphere totemperatures in excess of 1,000 Farenheit. Generally the wedge will havea greater malleability than the metallic knife edge tin and includedblade to ease the crimping operation and therein form the smooth surfacerequired for the knife edge fin. The wedge exhibits a lower Youngsmodulus than the metallic blade of the knife edge fin in order not to beas easily extruded or transformed during the crimping operation. Therepaired knife edge fin may be utilized within a compressor or turbineapplication and other applications.

As disclosed and depicted herein, the materials of construction forrepairing a knife edge fin as disclosed may be comprised of any metallicmaterials, for example a high tensile strength steel which aftercrimping within the groove formed upon the honed surface of thedegradated blade may be further enhanced for corrosive propertiesthrough anodizing the metallic surface or plating the surface with ahigh corrosionresistant material, such as nickel, cadmium or zinc.

Therefore, through utilization of the apparatus and method of thepresent invention, one is provided with a means for repairing orreplacing knife edge fins which are degradated due to extreme operatingconditions of the parts from which the components are removed. Inparticular, the major portion of the component part need not be reworkedor repaired. It merely requires the application of the method of thepresent invention in order to readily provide an improved part in arepaired state which may be placed within the apparatus from which itwas removed and utilized for a long service period thereafter.

The present invention has been described herein with reference toparticular embodiments thereof. It will be appreciated, however, bythose skilled in the art, that various changes and modifications may bemade without departing from the scope of the invention as set forthherein.

Therefore, we claim:

1. A method for repairing a knife edge fin,,said fin being formed of asharpened blade formed as a part of a component part to be sealed, whichcomprises:

a. honing the knife edge of the blade to form a flat surface thereacrossthe normally sharp blade;

b. reaming a groove in the upper portion of the blade,

through the flat surface;

c. placing a metallic wedge within the groove, said wedge having aheight which in combination with the height of the blade forms a knifeedge fin of the exact height of the blade and knife edge of the originalknife edge fin, said upper portion of said wedge being sharpened to forma knife edge; and

crimping the sides of the blade to close the groove about the wedge.

2. The method of claim 1 in which the knife edge fin is circular and thewedge is a circular band having a flat inner circumferential edge andthe external circumferential edge is sharpened to form the knife edge.

3. The method of claim 2 in which the knife edge fin is positioned onthe outside diameter of the part and further comprising:

a. heating the blade and groove contained therein prior to theintroduction of the wedge; and

b. cooling the wedge prior to its introduction into the groove.

4. The method of claim 3 in which the circular band has a greatermalleability than the circular metallic knife edge fin and includedblade.

5. The method of claim 4 in which the circular band exhibits a lowerYoungs modulus than the circular metallic knife edge fin and includedblade.

6. The method of claim 4 in which the metallic knife edge fin andincluded blade are precast and made more malleable than the circularband by malleabilizing the casting by annealing the casting to convertthe chemically combined carbon contained therein, at least partially,into free graphite carbon in rounded form.

7. The method of claim 2 in which the wedge has a greater malleabilitythan the metallic knife edge fin and included blade.

8. The method of claim 7 in which the wedge exhibits a lower Youngsmodulus than the metallic knfe edge fin and included blade.

9. Apparatus comprising a rebuilt metallic knife edge fin, said knifeedge fin originally being formed of a sharpened blade formed as a partof a component part -to be sealed, which comprises:

a. a blade having a honed knife edge forming a flat surface having agroove reamed therein; and

b. a metallic wedge, having a sharpened upper portion thereof forming aknife edge, and the lower portion thereof being crimped within thegroove of the blade.

10. The apparatus of claim 9 in which the knife edge fin is circular andthe wedge is a circular band having a flat inner circumferential edgeand an external circumferential edge being sharpened to form a knifeedge.

1. A method for repairing a knife edge fin, said fin being formed of asharpened blade formed as a part of a component part to be sealed, whichcomprises: a. honing the knife edge of the blade to form a flat surfacethereacross the normally sharp blade; b. reaming a groove in the upperportion of the blade, through the flat surface; c. placing a metallicwedge within the groove, said wedge having a height which in combinationwith the height of the blade forms a knife edge fin of the exact heightof the blade and knife edge of the original knife edge fin, said upperportion of said wedge being sharpened to form a knife edge; and crimpingthe sides of the blade to close the groove about the wedge.
 2. Themethod of claim 1 in which the knife edge fin is circular and the wedgeis a circular band having a flat inner circumferential edge and theexternal circumferential edge is sharpened to form the knife edge. 3.The method of claim 2 in which the knife edge fin is positioned on theoutside diameter of the part and further comprising: a. heating theblade and groove contained therein prior to the introduction of thewedge; and b. cooling the wedge prior to its introduction into thegroove.
 4. The method of claim 3 in which the circular band has agreater malleability than the circular metallic knife edge fin andincluded blade.
 5. The method of claim 4 in which the circular bandexhibits a lower Young''s modulus than the circular metallic knife edgefin and included blade.
 6. The method of claim 4 in which the metallicknife edge fin and included blade are precast and made more malleablethan the circular band by malleabilizing the casting by annealing thecasting to convert the chemically combined carbon contained therein, atleast partially, into free graphite carbon in rounded form.
 7. Themethod of claim 2 in which the wedge has a greater malleability than themetallic knife edge fin and included blade.
 8. The method of claim 7 inwhich the wedge exhibits a lower Young''s modulus than the metallic knfeedge fin and included blade.
 9. Apparatus comprising a rebuIlt metallicknife edge fin, said knife edge fin originally being formed of asharpened blade formed as a part of a component part to be sealed, whichcomprises: a. a blade having a honed knife edge forming a flat surfacehaving a groove reamed therein; and b. a metallic wedge, having asharpened upper portion thereof forming a knife edge, and the lowerportion thereof being crimped within the groove of the blade.
 10. Theapparatus of claim 9 in which the knife edge fin is circular and thewedge is a circular band having a flat inner circumferential edge and anexternal circumferential edge being sharpened to form a knife edge.